Conjugated compounds, or more in particular, thiophene-containing or furan-containing conjugated compounds are used in various industrial applications. For example, they can be used as dyes or pigments, as (semi)conductors, (electro)luminescent material or in electr(on)ical, optical and electro-optical devices such as light emitting diodes, field-effect transistors, solar cells, polarizing optical elements and batteries. In the context of the invention a compound is considered to be conjugated if, upon electronic excitation, it absorbs ultraviolet light or radiation of lower frequencies.
However, due to the inherent rigidity of the conjugated system, many potentially interesting conjugated compounds are insoluble. For many industrial applications processability from solution and therefore solubility is an essential requirement if an economically viable process is to be obtained.
To enhance the solubility of a conjugated compound it has been proposed to include solubilizing substituents such as large alkyl or alkoxy groups. However, this has the undesired side-effect that properties other than the solubility, such as the charge-carrier mobility, are adversely affected as well.
In order to enhance the processability from solution, it has also been proposed to use a method of the type mentioned in the opening paragraph. In such a method, referred to as a precursor method for short, the processing, such as, for example, the formation of a layer by spincoating, is done using the precursor compound. As a final step, the precursor compound is (thermally) converted by separating the separable substituents from the remainder of the compound thus forming the conjugated compound. Only a few conjugated compounds have been prepared by a method which uses such precursor compounds. One example is poly(2,5-thienylenevinylene) as disclosed in a publication by Kwan-Yue Jen et al. in J. Chem. Soc., Chem. Comm., 1987, p 309. Since the precursor method is a very attractive method of rendering conjugated compounds processable from solution, there still exists a need for methods of preparing a conjugated compound using precursor compounds.